Solid-state induced tautomerism in some arylazo derivatives of resorcinol

Abstract

The azo-hydrazone tautomerism of four arylazoresorcinols, where aryl is phenyl, naphthyl, p-nitrophenyl and o-nitrophenyl group, was studied using the UV–vis spectroscopy of solutions and solid substances, the X-ray crystallography and DFT calculations. In solutions, all the studied compounds exist predominantly as the azo tautomers. In crystals, the tautomeric equilibrium shifts toward the keto hydrazone form under the effect of intermolecular O–H⋯O hydrogen bonds. This conclusion is supported by analysis of the spectroscopic and crystallographic literature data.